Method of galvanizing



METHOD OF GALVANIZING Original Filed Nov. 25, 19:59

2 Sheets-Sheet l INVENTOR. ELW/N A MjfiTESO/Y 6M i A TTORNEYS March 28, 1944. MATTESQN 2,345,058

METHOD. or GALVANIZING Original Filed Nov. 25, 1939 2 Sheets-Sheet 2 l A V I3 zmazsva I LEAD Z/IVC [Evil INVENTOR. EL WIN A. MA 7' E50 ATTQRNEYS Patented Mar. 28, 1944 METHOD OF GALVANIZING Elwin A. Matteson, Youngstown, Ohio, assignor to The Aetna-Standard Engineering Company, Youngstown, Ohio, a corporation of Ohio Original application November 25, 1939, Serial No.

306,156. Divided and this application Septemher 1, 1942, Serial No. 456,891

2 Claims.

This invention relates to the art of metal coating and more particularly to certain improvements in methods of galvanizing, i. a, coating with zinc, steel sheets or strips. This application is a division of my copending application Serial No. 306,156, filed November 25, 1939, now Patent -No. 2,310,162, issued February 2, 1943.

In the galvanizing of steel or iron sheets or other articles it has been a common procedure to pass the sheets into and through a pot or tank of molten zinc to effect the bonding of a layer of pure zinc to all surfaces of the work. A modification of this general procedure is to establish and maintain a pot of molten lead and float upon a'portion of the surface of the pot of lead a layer or pool of molten zinc. The sheets are caused to enter and pass through the lead bath which brings them up to the'proper temperature and they are then withdrawn through the floating zinc body to apply zinc coating to the preheated articles. The lead does not adhere to the metal and serves merely as a pre-heating means. This arrangement eliminates the necessity of maintaining a large pot full of molten zinc and also achieves a better zinc coating because the preheated sheet is only subjected to contact with the zinc for a relatively short period and thus the alloy layer between the steel and zinc is kept to a minimum thickness. As this alloy layer is relatively brittle it is advantageous, particularly where the sheets are to be bent or formed after galvanizing, ,to maintain it as thin as possible.

In the galvanizing of ferrous metal articles dross is formed as the work passes through the zinc bath. This dross is composed largely of an alloy of zinc and iron, together with certain other impurities, and is heavier than zinc but lighter than lead. In the operation of a galvanizing pot having a pool of zinc floating on a bodyof lead, the dross settles down to the junction or common level of the lead and zinc where it floats upon the lead. in order to permit satisfactory continuous operation this dross must be removed. lAS

the operator is unable to see and gauge this leadzinc level, the removal of this dross presents a rather difficult problem, and it is among the obiects of my invention to provide an improved method of galvanizing sheet or strip metal wherein the dross may be continuously removed from the lead-zinc level.

Other objects of. my, invention include the provision of a simple method for improving and rendering more uniform the zinc coating applied by a galvanizing machine?" Another object is to provide a method of removing the dross which can be carried out without interfering with the galvanizing operations and in which the presence of a sheet or strip in-the bath does not interfere with the flow of the dross into a dross-collecting compartment.

The above and other objects of my invention will appear from the following description of a preferred embodiment thereof, reference being had to the accompanying drawings, in which-- Figure 1 is a plan view of a galvanizing pot and machine equipped with my apparatus and adapted. to carry out my method. 4

Figure 2 is a vertical cross-sectional view of the galvanizing equipment shown in Figure 1, taken substantially on line 2-2 of Figure'l.

Figure 3 is a transverse vertical cross-sectional view taken on line 3-3 of Figure 1, showing on of the dross moving screws.

'Figure 4 is a simplified illustrative vertical apparatus taken substantially on line 4-4 of Figure 1, but omitting numerous parts of the structure in order more clearly to show the arrangement of certain features of my invention.

Figure 5 is a diagrammatic cross-sectional view, on a reducedscale, taken on line 55 of Figure 4 and showing the disposition of the lead and zinc in the pot.

The tank or pot I has an open top and supports the spaced vertically extending frame members 2 and 3 which are connected together by suitable cross members such as the rods 4, the ends of which are secured to the Side frame members 2 and 3 by nuts 5 (see Fig. 2). The machine frame structure so formed supports the sheet feeding mechanism and also carries my improved dross skimming apparatus. The entire assembly makes upa galvanizing machine or unit which may. be lifted bodily from the pot i when so desired.

The mechanism for feeding the steel sheet or strip through the metal bath in the pot I may be of any suitable form and in the illustrated structure it includes a pair of entering rolls 6 and l which are located immediately below the entering power source and the shaft of the roll l2 carries a gear l9 meshing with a gear 20 which is also connected to the power source. Thev bottomroll I I is provided with a worm gear 2| meshing with "a worm 22 on the lower end of the drive shaft 23.

The upper end of shaft 23 carries a bevel gear 24 which is driven by a corresponding bevel gear 25 from the power source. Any suitable means may be provided for synchronizing the speeds of the three sets of rolls but, as this forms no part of the present invention, it is not illustrated or described herein. Furthermore, as the details of p the roll supports, etc., are not involved. in the present invention they need not be specifically described in great detail, but reference is made to Patent No. 2,183,890, issued December 19, 1939, on application of Elwin A, Matteson and Benjamin P. Finkbone, Serial No. 200,486, filed April 6, 1938, which fully illustratesand describes a similar arrangement of feed rolls and associated parts.

The usual flux box 26, which may be a walled structure open at the top and bottom, is disposed just below the entering rolls 6 and 1 and the walls extend from above the bath level down into the molten metal. A bafile or mud wall 21 extends entirely across the pot i and extends down from the top thereof well below the level of the molten metal. This wall 27,. as will more fully appear later, serves to separate the zinc pool from the body of molten lead in the pot and thus reduces the quantity of zinc required to be maintained in the not.

As is best seen in Figure 4, the pot is substantially filled with molten lead indicated at 26 and a relatively small pool of molten zinc 23 is maintained at the exit end of the pot and prevented from spreading over the entire surface of the molten lead by the wall 21; As zinc vis lighter than lead the zinc-lead level or junction 30, which cannot be observed by theoperator, may

' be maintained by properly maintaining the vissump is a separate compartment from the main pet I and, although it is shown on the drawings as being a structure extending beyond the main side wall of the pot I, it will be understood that it might be incorporated within the walls of the pot if so desired. A dross outlet pipe 34 extends from the bottom of the sump 33 to any suitable place of disposal and is provided with shut-E means such as a valve (not shown) to prevent the flow of material from the sump 33 except when it is desired to withdraw dross therefrom. The inner wall 35 of the sump 33 extends up to the normal lead-zinc level 30 and forms a dam preventing the entry of lead into the sump 33. The sump 33 will be filled with molten zinc as indicated in Figures 3 and and the lead-zinc level or dross line36' will not extend into the sump 33 but will stop at the wall 35.

It will be observed by referring to Figure 4 that, when sheet or stripmaterial is passed through the molten metal-- in the pot l by will first be heatedto the desired temperature as it passes through the lead bath 23. Then, as it enters the zinc pool 29 through the lead-zinc level and passes out through the exit rolls i2 and i3, it will be'given the desired zinc coating. The galvanizing operation causes the formation or dross inthe zinc bath 23 and this dross. will settle down to the lead-zinc level 30 where it 7 will float upon the surface of the lead. It is important to prevent the accumulation of dross at this level as it seriously interferes with successful coating of the work. In order positively and effectively to prevent the accumulation of dross at the lead-zinc level 30 I provide a pair of conveyor or feed screw members 36 and 31. These are disposed with their axes substantially at the lead-zinc level 30, the screw 36 being on one side of the path of the work through the zinc bath and the screw 31 being on the other side thereof. In the illustrated embodiment of my invention these screws 36 and 3'! are of opposite handand rotate in'opposite directions, thus moving the dross toward and into the sump 33.

The driven gear is on the exit roll i2 drives a gear 38, suitably supported on the frame 2, which in turn drives another gear 39. The shaft which carries the gear 38 also carries a sprocket 46 and a chain 4! drives the screw 36 through a suitable sprocket 40 mounted on the end of the screw shaft 42. In like manner, a driving connection is established to the shaft of the screw 3! through a chain 43 and suitable sprockets 43' and 43" connected to the gear 39 and the screw shaft 31' respectively.

The above described driving hook-up for the screws 36 and 31 will result in opposite rotation of the screws and therefore the screws are preferably made of opposite hand in order to cause a feeding action or flow of the material in the lead-zinc level 30 in a direction toward the dross sump 33. If desired both screws could, of course, be made the same hand and rotated in the same direction.

As is best seen in Figure 3, the shaft 31' of the screw 31 is supported in one end in a bearing 44 carried by the frame member 2. The frame 3 is provided with a suitable aperture 45 through which the screw 31 extends. The screw shaft 31" just clears the top of the inner wall 35 of the dross sump 33 andv this wall is preferably notched adjacent the shaft 31' so that the wall 35 will extend up to about the center line of the shaft 31'. A hearing bracket or hanger 46 is suspended on a projecting arm 41 mounted on the frame 3' and this bracket 46 carries a bearing 48 which supports the other end of the screw shaft 31' within the dross sump 33,

The screw 36 and its shaft 42 are similarly. mounted and a suitable aperture is provided in the wall 3 for the screw 36. This aperture may be an elongated slot or a series of holes may be provided so that the dross flow of movement, established by rotation-of-the screws 36 and 31,

- in a direction across the bath toward the sump meansof the rolls 6'|, Iii-ll and |2--l3, it

33 will not be seriously interfered with by the wall 3. It will be understood that rotation of the screws 36 and 31 will set up a flow of dross not only within the radius of the screws themselves but also for a certain distance on either side thereof. This dross,'.as it moves across the surface of the lead bath, will pass over the top of the wall 35 into the dross sump 33, which as the direction of movement of the sheet is not interfered with in any way by the sheet. Moreover, by providing a pair of feed screws 36 and 31, the dross which is formed and collects at the lead-zinc level on both sides of the sheet path is removed. v

Even though the lead-zinc level 30 may vary both sides of the sheet or strip insures the production of uniform coatings, and the method results in increased output of galvanzed sheets or r the like, with improved results.

Although I have described the illustrated apparatus and certain preferred procedures in considmaterially in a downward direction from the top of the wall 35 the screws 36 and 31 will still be effective so long as the level does not vary more than the eifective radius of these screws. This fact eliminates the necessity for maintaining the lead-zinc level 30, which cannot be seen-by the operator, with extreme accuracy as normal variations will not interfere with the effective removal of the dross. If the lead-zinc level 33 drops below the top of the wall 35 the dross will merely build up against the wall 35, due to the action of the screws 31, and, as the screws continue to rotate, will be pushed on over the wall into the sump 33. Care should, of course, be taken to prevent the lead level from rising above the level of the top of the wall 35 so that the lead will not flow into the sump 33, although, in case this should happen, it can be readily corrected by lowering the lead' level to the proper position and then drawing off any lead which has accumulated in the sump 33.

According to my preferred method, which is preferably carried out by an apparatus such as that described'above, the work is passed" througha lead bath and then upwardly through a layer of zinc floating on the lead. The dross formed in the galvanizing operation floats at the lead-zinc dross does not interfere with the movement of the erable detail it will be understood by those skilled in the art that variations and modifications may be made in the same without departing from the spirit of my invention. I do not, therefore, wish to be limited to the particular embodiment of my 1 invention shown and described, but claim as my invention all forms thereof coming within thescope of the appended claims.

I claim:

1. In the galvanizing of metal sheets or strips, a process which includes the steps of passing a sheet or strip into a bath of molten lead having a pool of molten zinc floating thereon at a point removed from the point of entry of the sheet or strip into the lead bath, removing 'the sheet or strip from the bath through the pool of zinc, and removing dross from the lead-zinc level of the bath by causing the dross to move in a horizontal direction generally parallel to and on both of the side surfaces of the sheet or strip as it passes through said lead-zinc level.

2. In the galvanzing of metal sheetsor strips, a process which includes the steps of passing a sheet or strip into a bath of melted lead having a a pool of molten zinc floating thereon at a point removed from the point of entry of the sheet or strip, removing the sheet or strip from the bath through the pool of zinc. and removing dress from the lead-zinc level of the bath by causing the dross to move in a direction generally parallel to the side surfaces of the sheet or strip and transverse to the direction of movement of the sheet as it passes through said lead-zinc level.

ELWIN A. MATTESON.

work; The continuous removal of the drossfrom 

